The present invention relates to an exposure apparatus such as an exposure apparatus (so-called a stepper) for sequentially projecting and forming an electronic circuit pattern on a reticle surface onto a wafer surface by step & repeat exposure via a projection optical system in the manufacture of semiconductor elements such as ICs, LSIs, and the like, an exposure apparatus (so-called a scanner) for similarly sequentially projecting and forming an electronic circuit pattern on a reticle surface onto a wafer surface by step & scan exposure via a projection optical system, and the like, and so on, and a device manufacturing method that uses the exposure apparatus and, more particularly, to an exposure apparatus used in the manufacture of semiconductor elements, which is hardly influenced by deformation of the main body structure by detecting in advance the relationship between the deformation state of the main body structure and stage precision, and in actual exposure adequately measuring the deformation state and correcting the alignment measurement value and alignment position of a shot in real time, and a device manufacturing method using the apparatus.
The present invention further relates to a high-speed, high-precision alignment stage apparatus which can be suitably applied to, e.g., reticle and wafer moving stages of semiconductor exposure apparatuses, an exposure apparatus having the alignment stage apparatus, and a device manufacturing method of manufacturing a device using this exposure apparatus.
In recent years, as semiconductor integrated circuits such as ICs, LSIs, and the like continue to shrink in feature size, a projection exposure apparatus is required to have further improved image performance, superposing precision, throughput, and the like. The superposing precision can be roughly classified into global components of the shot matrix within a wafer and components within each shot. The former components can be generally subdivided into a wafer shift component, wafer magnification component, wafer rotation component, orthogonality component, and the like. The latter components can be generally accounted for by a shot (chip) magnification component, shot (chip) distortion component, shot (chip) rotation component, and the like. Among these errors, error components produced by deformation of the main body structure have gradually surfaced due to improvements of the apparatus performance.
The error components produced by deformation of the structure are classified into static components reproduced every time wafer and reticle stages move, and dynamic components such as heat, repulsive force due to step & scan exposure, and the like, which are hard to reproduce.
In order to remove these error components, conventionally, the rigidity of the main body structure is increased; a structure which does not deform even when an external force is slightly applied to the structure, or a structure which does not follow disturbance vibrations due to raised natural frequency is exploited. However, as the rigidity of the main body increases, the weight increases accordingly, and a design that can attain both a weight reduction and high rigidity becomes hard to achieve. When a product is designed in consideration of only high rigidity of the main body, evidently the weight of the main body becomes large, and the obtained product is hard to handle in terms of carrying out/in, installation, and the like of the apparatus.
As measures against heat that have been conventionally taken, the heat source of the apparatus is cooled, its heat generation amount is reduced, a low thermal expansion material is used in a structure, and so on. However, there are more than one heat source in the apparatus, and it is impossible to cool all these sources. Furthermore, even when measures against heat conduction or transfer from the heat sources are taken, an effective measure cannot often be taken for radiation, and thermal influences remain unsolved. Also, the use of a low thermal expansion material in the structure results in higher cost than a normal material, and yet the thermal influences of the heat sources cannot be perfectly removed.
As described above, deformation factors of the main body include dynamic factors such as vibrations, forces, and the like, and thermal factors.
In the former factors, dynamic and static deformations attributed to the repulsion forces of the stages that support the main body structure, and dynamic and static deformations caused by a vibration control/vibration reduction device used for the purpose of controlling vibrations of the main body upon driving of the stages have large components. Of these components, alignment measurement data, print data, and the like indicate that the deformation component due to the force applied to the main body by the vibration control/vibration reduction device to control vibrations of the main body is by no means negligible. Since this deformation component is inevitable in terms of the function of the vibration control/vibration reduction device as long as the stages are driven, it is impossible to set the deformations of the main body structure to zero.
The latter factors include changes in ambient temperature, changes in temperature of various heat sources, and the like. Especially, a non-steady process from when the thermal equilibrium state is broken until the thermal equilibrium state is reached again is important for the thermal factors. Since it is impossible to perfectly recognize the thermal behaviors of the individual heat sources and a cooling source such as air in the apparatus, such a non-steady process is produced more or less as long as the apparatus is in operation and processing wafers. Hence, it is impossible to set deformations of the main body structure arising from thermal expansion or shrinkage to zero.
On the other hand, alignment stage apparatuses used in semiconductor exposure apparatuses are required to have high alignment precision in order to mount position control targets such as wafers and reticles, and thus widely adopt a stage position measurement means using a combination of a high-resolution laser interferometer and laser mirror.
However, since the position control point and position measurement point do not coincide with each other, deformations arising from changes in temperature and changes in stress cause position measurement errors.
To solve this problem, Japanese Patent Laid-Open No. 4-291910 discloses a method of correcting variations in distance between the position control point and position measurement point. More specifically, as shown in FIG. 26, variations in distance between a laser mirror 2101 as a position measurement target and a wafer 2102 as a position control target are measured by an electric micrometer 2106, and the measurement values are added to an alignment laser target value.
Even this method cannot correct measurement errors produced by deformation and inclination of a fixing jig 2105 for fixing the electric micrometer 2106 to a top table 2104. That is, since measurement errors cannot be completely corrected as far as an additional critical dimension measurement sensor is used, variations in distance between the position control point and position measurement point must be accurately corrected without using any additional critical dimension measurement sensor.
Of these errors, measurement errors due to changes in temperature can be prevented by using a low thermal expansion material, a temperature adjustment device, and the like. However, high stage speeds for a short moving time increase measurement errors due to elastic deformation, so that demands have arisen for correction of variations in distance due to elastic deformation of the stage.
It is still another object of the present invention to correct alignment measurement errors, focus measurement errors, stage position measurement errors, and the like arising from elastic deformation of a projection main body structure in real time in consideration of the fact that the elastic deformation and measurement errors due to the elastic deformation represent the linear sum of operating forces which cause the elastic deformation.
It is still another object of the present invention to accurately correct variations in distance between the position control point and position measurement point due to elastic deformation of the stage.